Always difficult to post a review when you don't have any specialist knowledge on the subject or even too much experience with other headphones. As such, I am sure others will give the precise details and technical reviews.
However, I purchased these headphones as I needed a decent set without breaking a rather limited budget.
My first experiences are that they are a reasonable set of headphones. The sound quality seems excellent and when on, do seem to cut down on the outside noise levels (I am not sure I could not say 81% based on my washing machine test). They are reasonably comortable and adjust well enough.
The build quality seems decent enough and they certainly don't feel cheap to me.
They did not distort the sound, so all in all I would recommend them. And John Lewis sell them at almost twice the price - so if they are good enough for JL they good enough for me!